Retroreflective pavement markers are used to provide a reflected signal for marking traffic lanes and for edge delineation at night and particularly under adverse weather conditions. The term "retroreflector", as used herein, refers generally to reflectors adapted to reflect light emanating from an oncoming vehicle back toward the vehicle. Various types of retroreflective elements are known, and may include cube-corner type reflectors, lens-mirror devices, beaded sheet, cube-corner type sheeting, and other retroreflective devices.
Pavement markers may be classified generally as either of a "moving" or "depressible" type (typical examples of such markers being disclosed in U.S. Pat. Nos. 2,941,447; 3,093,038; 3,216,335; 3,373,667; and 4,130,370; and British Pat. Nos. 648,542 and 614,657) or of a non-moving, self-cleaning type (such as disclosed in Heenan U.S. Pat. No. 3,332,327, assigned to applicant's assignee). Copies of all the foregoing patents accompanied the filing of the parent to this application.
Prior art pavement markers, particularly the depressible type referred to hereinabove, generally have involved moving parts and expensive castings in an attempt to make them both depressible and self-wiping, and all have encompassed several parts to achieve that function. As an example, they may require springs or other component parts set in separate castings and provided with a depressible portion, or they may involve a rubber-type surface also set in a metal casting of some character. Those prior art depressible type markers are expensive to produce and install. Additionally, in many instances, those prior art markers are not capable of sustaining repeated impact of studded tires on the reflective elements. Also, partly extending above the roadway surface, they are subject to severe damage by snow-plow blades.
The rigid or non-moving self-cleaning type markers, such as found in Heenan U.S. Pat. No. 3,332,327, and the snowplowable versions of that marker, also disposed in metal castings and positioned slightly above the roadway surface, provide an extremely effective marking system. However, when used with a metal casting, they also are relatively costly to produce and install as compared to the nonsnowable use which does not require the metal casting. Also, the angled front face of those type of markers, intended to be wiped by the tires of oncoming vehicles to keep them clean, exposes the front surface to damaging impact by tire studs, and therefore they are not used in those areas where studded tires are regularly used.
In the past several years there has been experimentation by several states in snow-plow areas, in placing existing markers, such as those disclosed in the aforesaid '327 patent, in elongated grooves cut in the roadway surface. One expected advantage of this groove-marker system is the elimination of the metal casting used in snow-plow areas, and also this results in recessing the marker below the roadway surface to avoid impact by snow plow blades. But even when recessed in grooves, those markers are still subject to damage by studded tires and, being recessed, they may not be wiped as effectively as units directly on the roadway surface.
Accordingly, a primary object of the present invention is to provide an inexpensive simple, self-cleaning, easy to install depressible-type pavement marker which can be used on roadways serviced by snowplows.
It is a further object of the present invention is to provide a pavement marker of the type described which is depressible when contacted by the tire of a vehicle passing thereover, so that the tire causes the marker to effect a wiping and cleaning action during said movement, whereby the marker can retain a relatively high percentage of its reflective capabilities over an extended period. In this regard, it is anticipated that the deterioration of reflectivity will be less for the depressible marker of the present invention than for immovable type markers subject to the direct abrasive action of tires.
It is a further object of the invention to provide a depressible and self-cleaning pavement marker of the type described which further includes means for protecting the retroreflector lens means from damage from the sharp pointed edges of studs typically employed on winter snow tires.
It is a further object of the invention to provide, in a pavement marker of the character described, a body member integrally formed of an elastomeric material which is depressible and will resiliently return to a non-depressed reflective position, and which further includes wiping means integrally formed therewith and retroreflective lens means carried by a portion of the body member, and which requires no additional housing or casting for placement on the associated roadway.